[stdlib] Fix the example in LazySequenceProtocol docs.
[stdlib] Fix the example in LazySequenceProtocol docs.

I'm not sure this code ever worked, but this new version does. Also
includes some style revisions to the surrounding text.

glessard/swift,hooman/swift,atrick/swift,nathawes/swift,gregomni/swift,karwa/swift,CodaFi/swift,xwu/swift,apple/swift,gribozavr/swift,lorentey/swift,harlanhaskins/swift,roambotics/swift,benlangmuir/swift,hooman/swift,karwa/swift,sschiau/swift,devincoughlin/swift,jmgc/swift,lorentey/swift,devincoughlin/swift,ahoppen/swift,allevato/swift,sschiau/swift,allevato/swift,CodaFi/swift,karwa/swift,nathawes/swift,benlangmuir/swift,hooman/swift,roambotics/swift,ahoppen/swift,tkremenek/swift,apple/swift,glessard/swift,parkera/swift,allevato/swift,gribozavr/swift,tkremenek/swift,xwu/swift,stephentyrone/swift,karwa/swift,atrick/swift,sschiau/swift,gregomni/swift,jmgc/swift,roambotics/swift,JGiola/swift,hooman/swift,aschwaighofer/swift,lorentey/swift,stephentyrone/swift,xwu/swift,stephentyrone/swift,apple/swift,apple/swift,glessard/swift,tkremenek/swift,parkera/swift,rudkx/swift,lorentey/swift,karwa/swift,jmgc/swift,jmgc/swift,allevato/swift,gribozavr/swift,ahoppen/swift,aschwaighofer/swift,xwu/swift,rudkx/swift,aschwaighofer/swift,airspeedswift/swift,gribozavr/swift,rudkx/swift,rudkx/swift,JGiola/swift,harlanhaskins/swift,sschiau/swift,CodaFi/swift,stephentyrone/swift,allevato/swift,tkremenek/swift,karwa/swift,devincoughlin/swift,parkera/swift,parkera/swift,apple/swift,JGiola/swift,roambotics/swift,harlanhaskins/swift,airspeedswift/swift,tkremenek/swift,glessard/swift,ahoppen/swift,jmgc/swift,rudkx/swift,gregomni/swift,lorentey/swift,tkremenek/swift,benlangmuir/swift,lorentey/swift,hooman/swift,nathawes/swift,gregomni/swift,lorentey/swift,rudkx/swift,JGiola/swift,parkera/swift,CodaFi/swift,xwu/swift,devincoughlin/swift,jckarter/swift,airspeedswift/swift,jckarter/swift,sschiau/swift,parkera/swift,benlangmuir/swift,hooman/swift,jckarter/swift,tkremenek/swift,atrick/swift,jckarter/swift,sschiau/swift,gribozavr/swift,parkera/swift,stephentyrone/swift,airspeedswift/swift,atrick/swift,CodaFi/swift,benlangmuir/swift,allevato/swift,harlanhaskins/swift,ahoppen/swift,parkera/swift,gribozavr/swift,apple/swift,aschwaighofer/swift,jckarter/swift,gregomni/swift,ahoppen/swift,JGiola/swift,CodaFi/swift,devincoughlin/swift,lorentey/swift,harlanhaskins/swift,roambotics/swift,jckarter/swift,airspeedswift/swift,hooman/swift,xwu/swift,atrick/swift,gribozavr/swift,xwu/swift,nathawes/swift,devincoughlin/swift,jckarter/swift,karwa/swift,benlangmuir/swift,aschwaighofer/swift,harlanhaskins/swift,jmgc/swift,nathawes/swift,sschiau/swift,devincoughlin/swift,stephentyrone/swift,stephentyrone/swift,glessard/swift,aschwaighofer/swift,sschiau/swift,harlanhaskins/swift,CodaFi/swift,gribozavr/swift,aschwaighofer/swift,glessard/swift,nathawes/swift,airspeedswift/swift,nathawes/swift,devincoughlin/swift,JGiola/swift,roambotics/swift,atrick/swift,airspeedswift/swift,jmgc/swift,karwa/swift,gregomni/swift,allevato/swift